GitHub user zsxwing opened a pull request:
https://github.com/apache/spark/pull/8340
[SPARK-10137][Streaming]Avoid to restart receivers if scheduleReceivers
returns balanced results
This PR fixes the following cases for `ReceiverSchedulingPolicy`.
1) Assume there are 4 executors: host1, host2, host3, host4, and 5
receivers: r1, r2, r3, r4, r5. Then
`ReceiverSchedulingPolicy.scheduleReceivers` will return (r1 -> host1, r2 ->
host2, r3 -> host3, r4 -> host4, r5 -> host1).
Let's assume r1 starts at first on `host1` as `scheduleReceivers`
suggested, and try to register with ReceiverTracker. But the previous
`ReceiverSchedulingPolicy.rescheduleReceiver` will return (host2, host3, host4)
according to the current executor weights (host1 -> 1.0, host2 -> 0.5, host3 ->
0.5, host4 -> 0.5), so ReceiverTracker will reject `r1`. This is unexpected
since r1 is starting exactly where `scheduleReceivers` suggested.
This case can be fixed by ignoring the information of the receiver that is
rescheduling in `receiverTrackingInfoMap`.
2) Assume there are 3 executors (host1, host2, host3) and each executors
has 3 cores, and 3 receivers: r1, r2, r3. Assume r1 is running on host1. Now r2
is restarting, the previous `ReceiverSchedulingPolicy.rescheduleReceiver` will
always return (host1, host2, host3). So it's possible that r2 will be scheduled
to host1 by TaskScheduler. r3 is similar. Then at last, it's possible that
there are 3 receivers running on host1, while host2 and host3 are idle.
This issue can be fixed by returning only executors that have the minimum
wight rather than returning at least 3 executors.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/zsxwing/spark fix-receiver-scheduling
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/8340.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #8340
----
commit 5fba8d46db62118711ff965efc6c6772ba1ddd1b
Author: zsxwing <[email protected]>
Date: 2015-08-20T10:25:54Z
Avoid to restart receivers if scheduleReceivers returns balanced results
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